Field of Invention
The present invention relates to a field of stainless steel welding, and more particularly to a butt-joint welding method for stainless steel facilities or pipes, suitable for forming and welding root passes.
Description of Related Arts
During a process of welding the stainless steel weldment, due to the high content of alloy, the metal in the weld pool has a poor liquidity, which tends to generate various welding defects. Especially for welding the root welding seams of the stainless steel facilities or pipes, without the cleaning treatment, the root welding seams are liable to suffer from the incomplete penetration and the lack of fusion, as well as the oxidation at the backs of the welding seams.
Conventionally, the shielded metal arc welding (SMAW) and the gas tungsten arc welding (GTAW) are capable of solving the oxidation at the backs of the welding seams. However, the SMAW has a difficulty in the formation of the backs of the welding seams; a high current would induces a low weld pool, and be liable to penetrate the weldment or generate an overlap at the back of the welding seam; and a low current would induces a shallow fusion depth, the incomplete penetration and the lack of fusion. Although the GTAW well accomplishes one-side welding with back formation, the back of the welding seam requires the protection from argon, otherwise the welding seam would be oxidized, which reduces the strength of the welding seam and the resistance to corrosion and blackens the appearance. Adopting the GTAW and filling the argon to protect the back of the welding seam both greatly increase the welding cost, especially in the butt-joint welding of the slim pipes, and also greatly affects the heath, the safety and the working environment of the welders.